EVALUATION OF ROOTSTOCKS FOR ‘ TAHITI ’ ACID LIME IN NORTHERN STATE OF MINAS GERAIS 1

the aim of this study was to evaluate 12 rootstock varieties on the development and quality of ‘tahiti’ acid lime fruits cultivated in the municipality of Jaíba, mG. Seedlings were planted in an experimental orchard in November 2008, using 8 x 5 meters spacing and drip irrigation. the experiment was conducted using a scion cultivar (tahiti acid lime, IaC-5 cultivar) and the following 12 rootstocks: ‘Rangpur’ lime, ‘troyer’ citrange, ‘Carrizo’ citrange, 1707 hybrid (Rangpur lime x Swingle trifoliate), 1710 and 1697 citrandarins, 1708citradia, ‘Swingle’ citrumelo, ‘Cleopatra’ and ‘Sunki’ mandarins, ‘volkamer’ lemon, and ‘Limeira’ trifoliate. A randomized block design with five replicates and three trees per plot was used. trunk diameter of both rootstock and scion, as well as height, diameter, and canopy volume, yield, fruit mass, number of fruits per tree, productivity, production efficiency index, longitudinal diameter, equatorial diameter, total soluble solids, total acidity, and vitamin C content of fruits were evaluated. ‘volkameriano’ and ‘Cleopatra’ rootstocks promoted higher plant vigor and productivity for ‘tahiti’ acid lime. however, ‘Limeira’ trifoliate and ‘Troyer’ citrange produced less vigor, but increased production efficiency; and can be used as alternative rootstocks for ‘Rangpur’ lime, as long as adjustments are performed in the planting spacing to increase productivity. In general, no differences in physical and chemical characteristics of fruits for all treatments were found, and fruits remained within commercial standards.


INTRODUCTION
'tahiti' acid lime (Citrus latifolia tanaka), popularly known in Brazil as tahiti lemon, has emerged as an alternative to sweet orange producers due to its good adaptation to tropical climatic conditions and greater economic value (RODRIGueS et al., 2016).
according to data from agrianual (2014), Brazilian production was 1,165,296 tons of lemons in 2013.the southeastern region is the main national producer, and the State of São Paulo is the largest Brazilian producer, followed by minas Gerais.the Northern Region of the State of minas Gerais has increased its participation in this market, with production of 'tahiti' acid lime exponentially growing in the region.Part of the production is exported, which has increasingly aroused producers' interest in this crop.
Despite the commercial importance of acid lime, there is little research on the fruit in the region of the Irrigated Perimeter of Jaíba and, consequently, little availability of data to assist the producer in the decision making in the time of planting, in order to obtain better returns.
One of the problems in the region refers to the fact that crops are based almost exclusively on the use of plants grafted on 'Rangpur' lime due to the tradition of using this rootstock, the lack of seedlings grafted on other rootstocks and the lack of research that indicates alternative rootstocks.although 'Rangpur' lime is considered a rootstock suitable for 'tahiti', it is susceptible to gummosis caused by Phytophthora citrophthora and Phytophthora parasitica, which reduces plant longevity (CaRvalhO et al., 2016).In addition, plants grafted on 'Rangpur' lime tree reach excessive sizes in the climate of northern minas Gerais, which requires the use of wide spacing or pruning.
Rootstocks influence about 20 horticultural characteristics of citrus, namely: absorption, synthesis and use of nutrients, size, production precocity, maturation, weight and permanence of fruits in the plant, bark and juice color, fruit productivity and quality (POmPeu JÚNIOR et al., 2013).therefore, it is important to select rootstocks suitable for the production system to be implanted in each region.the selection of alternative rootstocks is essential for the Brazilian citrus industry, as it may make orchards less vulnerable to the appearance of new pests that may affect the few varieties of rootstocks currently used (PetRY et al., 2015).
No studies carried out with rootstocks for 'tahiti' lime in minas Gerais have been found in literature.In Brazil, there are few researches carried out with this objective.Figueiredo et al. (2002), working with ten alternative rootstocks to 'Rangpur' lime tree in the region of Bebedouro, recommended 'Orlando' tangelo, 'morton' citrange, 'Swingle' citrume, 'volkameriano' lime and 'limeira' trifoliate.On the other hand, Stenzel and Neves (2004) observed that 'tahiti' plants grafted on 'Rangpur' lime and 'C-13' citrange presented the highest accumulated yields.
thus, the aim of this work was to evaluate the influence of 12 rootstocks on the development and quality of 'tahiti' acid lime fruits grown in the municipality of Jaíba, mG.

MATERIAL AND METHODS
the experimental orchard was planted in November 2008 in the Irrigation District of mocambinho, municipality of Jaíba, experimental Farm of mocambinho, technological Center of Northern minas Gerais / ePamIG.the coordinates are 15 o 03'S, 44° 01' W and 452 m asl. the climate of the region is a w type, according to Köppen classification, and climatic data (average of 10 years) are as follows: average maximum temperature: 34.0 ºC; average minimum temperature: 14.8 ° C; average temperature: 24.2 ° C; relative humidity: 58% to 79%; sunshine: 2,892 hours / year; precipitation: 787 mm / year; wind speed: 35 to 81 km / h. the predominant soil in the region is the dystrophic Yellow latosol and the predominant relief is flat.Previous soil physical analysis showed that the soil of the experimental area is of sandy texture, being composed of 76% of sand, 10% of silt and 14% of clay.
twelve treatments (rootstocks) and five replicates were used, each experimental unit consisting of three useful plants, comprising 60 experimental units, with a total of 180 useful plants.the external border was formed by 'tahiti' acid limes grafted on 'Rangpur' lime.Plants were arranged in 8m x 5m spacing and irrigated by the drip system.the experimental design was in randomized blocks.
the experiment consisted of a canopy cultivar (tahiti acid lime, IaC-5 -Citrus latifolia tanaka) and 12 rootstocks.the rootstocks were ''Rangpur' lime [C. limonia L. Osbeck] vegetative development was evaluated in the first semester of each year.The following parameters were evaluated from each tree under study: stem diameter of rootstock (DCPe, in mm) and graft (DCe, in mm), measured at 5 cm below and above the grafting point, respectively, plant height (a, in m), measured from the soil to the top of the plant and the canopy diameter (DCO, in m) measured perpendicular to the planting line.the average canopy volume (vmC, in m 3 ) was determined using the diameter and canopy height measurements using the formula of Mendel: V = 2/3 π x R² x A, where V is the canopy volume (m 3 ), R is the radius (m), π = 3.141593 and a is the plant height (m).
Fruits were harvested when they were fully developed, but with the green and slightly rough peel, which is the harvest point commercially used in the region.Due to the fact that 'tahiti' lime tree presents flowering multiplicity, harvests and production weighing were carried out throughout the year and the results of production per plant are summed and presented in the form of a value per year.the following production-associated variables were studied for each canopy / rootstock combination: yield per plant (PP, in kg), mean fruit mass (mmF, in grams), number of fruits per plant (NFP), productivity (PtvD, t.ha -1 ) and production efficiency (eP, in kg.m -3 canopy), calculated by dividing the average yield of each canopy / rootstock combination by the respective canopy volume.
Fruit quality was analyzed close to the main crop of the canopy cultivar, evaluating the physical and chemical characteristics of fruits.all fruit analyses were carried out at the laboratory of Fruit analysis, viçosa, mG, in the years 2011, 2012 and 2013, where the external quality attributes of 20 fruits per treatment were evaluated: diameter in the longitudinal direction (Dl, in mm) and diameter in the equatorial direction (De, in mm).
later, evaluations of attributes associated to the internal quality of the fruits were carried out: soluble solids content (SS, in ºBrix); titratable acidity (AT, in % citric acid); vitamin C content (TVC, in mg.100 ml -1 of juice) and yield in juice: RS (%).
Data were analyzed using Saeg 9.1 software (SaeG, 2014).analyses of variance were performed and when there were significant differences, the means of treatments were compared by the tukey test, adopting 5% of probability level.

RESULTS AND DISCUSSION
Regarding plant height, it was observed that, during the evaluation years, '1708' citradia, 'Cleopatra' mandarin and 'limeira' trifoliate rootstocks, with emphasis on the latter, induced smaller canopy size.there is a growing interest of researchers and producers for dwarfing rootstocks, which, above all, lead to a reduction in the harvesting cost, which is one of the most costly activities in the citrus production system.Some authors have related reduction of canopy vigor on dwarfing rootstocks to the lower water potential in the canopy, probably due to the difficulty in transporting water from roots to shoots (FORNeR-GuINeR et al., 2014).In addition, these rootstocks facilitate pest and disease management and increase productivity through planting densification (POMPEU JÚNIOR et al., 2013).
In the last evaluation carried out in 2015 when plants were seven years old, it was observed that the height of 'tahiti' plants on 'limeira' trifoliate (mean of 3.66 m) was 28% lower than the height of plants grafted on 'Swingle' citrumelo, which presented the highest mean height (5.08 m) this year.Plants on 'troyer' citrange, 'Rangpur' lime and '1708' citradia also stood out among the highest ones (taBle 1).
No significant differences among rootstocks were observed regarding stem diameter and rootstock in the years 2009 and 2010.From 2011, it was observed that rootstocks induced significant differences for these characteristics, with emphasis on 'Rangpur' lime and 'volkameriano' lemon, which induced higher values, as well as an increase in diameter of the graft stem that exceeded the diameter of the rootstock stem in the last years evaluated (taBle 1).
In the DCPe / DCe ratio, there was a general trend over the years of evaluations, where plants on 'Rangpur' lime, '1707' hybrid and 'Carrizo' citrange rootstocks had the lowest values.the greatest difference between rootstock and canopy diameters occurred in plants on 'limeira' trifoliate and '1708' citradia.this characteristic is commonly observed when rootstocks of the genus Poncirus trifoliate or their hybrids are used.For the other rootstocks studied, the ratio remained close to 1, indicating similar diameters (taBle 1).Plants on '1707' hybrid, '1710' citrandarin, 'Rangpur' lime and 'Swingle' citrumelo showed larger canopy diameters compared to the others (5.87 m, 5.27 m, 5.68 m 5.67 m, respectively, in 2015) in the last three years of evaluation, differing from 'limeira' trifoliate rootstock, which presented the lowest values in the last three years (3.05  m, 4.13 m and 4.54 m, In 2013, 2014 and 2015,  respectively) (taBle 1).Considering that 'tahiti' acid lime can reach up to 4.5 m in height, impairing crop and harvest management (azeveDO et al., 2015), a dwarfing rootstock such as 'Limeira' trifoliate emerges as promising for the northern region of minas Gerais, where favorable climatic and management conditions enhance the vegetative development of 'tahiti' acid lime tree.
In studies conducted by Figueiredo et al. (2002), in Bebedouro-SP, the authors found that 'volkameriano' 'Catania 2' lemon and 'Orlando' tangelo promoted greater development of the 'tahiti' canopy, with maximum value of 123.83 m 3 of average canopy volume in plants with nine years of age, and most values were close to those reported in this work in plants still at seven years of age.It is important the selection of rootstocks that induce the formation of smaller canopies, with high productive efficiency in relation to their volume, so as to allow the formation of more dense plants and to obtain greater production by area (SaNtOS et al., 2015) .
In this aspect, 'limeira' trifoliate and '1708' citradia, despite having induced the formation of smaller 'tahiti' canopy volumes in almost every year evaluated, in 2015, they induced higher production efficiency (1.29 kg.m -3 and 1.77 kg.m -3 , respectively) when compared to 'volkameriano' lime (0.95 kg.m -3 ) and 'Rangpur' lime (1.15 kg.m -3 ) (taBle 2), which indicates the possibility of being used in more densified plantations, providing greater production per area.these results corroborate Portella et al. (2016), who observed that 'limeira' trifoliate reduced height, vegetative vigor index, coverage rates in the row and inter-rows, and canopy volume of 'tahiti' acid lime in irrigated cultivation under the climatic conditions of northern Rio de Janeiro.lima, et al. ( 2014) also observed in northern Rio de Janeiro that the size of 'Lima' orange tree was reduced by 56% when grafted on 'limeira' trifoliate, having 'Rangpur' lime as reference in irrigated cultivation.
In the accumulated of the six harvests, 'Rangpur' lime was the most productive, with production of 90.73 kg.plant -1 in the last evaluation, in 2015, which represented production 98% above the rootstock that induced the lowest production, which was 'Cleopatra' mandarin (taBle 2).'volkameriano' lemon and 'Carrizo' citrange rootstocks, despite being little used in the region, were among the two that induced higher yields, indicating good adaptation to the edaphoclimatic conditions of Jaíba.another aspect to consider is that, although 'limeira' trifoliate and '1708' citradia rootstocks are not among the most productive in this work, they have reduced the vigor of plants and will probably require adjustments in the spacings in order to optimize soil utilization and increase productivity.
All production variables presented significant differences in the F test at 5% probability level in at least one year of evaluations (taBle 2).Regarding the annual production per plant, differences in rootstocks were observed from 2010.In 2013, production ranged from 52.08 to 70.76 kg.plant -1 for the 'troyer' citrange and 'volkameriano' lemon, respectively (taBle 2).Plants grafted on 'Rangpur' lime showed production in 2015 of 90.73 kg.plant -1 and those on 'Swingle' citrumelo, 70.00 kg.plant -1 .the latter is a well-known and widely used rootstock for citrus growers in the region and occupied an intermediate position in this experiment.
Analyzing the mean mass of fruits, the first evaluation showing significant differences was in 2011.In this evaluation, 'Cleopatra' mandarin rootstock induced the highest value (82.12 g), but this trend was not confirmed in evaluations in the following years (taBle 2). the fresh fruit mass values were lower than those reported by Stuchi et al. (2009), who obtained average values of 91 g, while in the present study, the mass values ranged from 71.17 to 82.12 g.
Table 2 shows significant differences among treatments in relation to the number of fruits per plant in all evaluation years.there is also an increase in the production of fruits per plant over the years.This is because 'Tahiti' produces flowers and fruits in new growing branches, so production is directly associated with the vegetative development of plants.the highest NFP (910) was obtained in 'tahiti' lime trees grafted on 'Rangpur' lime in the year 2015.In the same year, the lowest NPF was induced by DOI 10.1590/0100-29452017 790 Jaboticabal -SP EVALUATION OF ROOTSTOCKS FOR 'TAHITI' ACID LIME...

'limeira' trifoliate (496) (taBle 2).
In relation to PTVD, significant differences among rootstocks were observed from the second year of production.the highest yields were obtained on 'Rangpur' lime rootstocks (mean of 22.68 t.ha -1 per harvest in 2015), 'volkameriano' lemon (mean of 20.80 t.ha -1 per harvest In 2015) and 'Carrizo' citrange (average of 20.87 t.ha -1 per harvest in 2015), in contrast to 'Sunki' and 'Cleopatra' mandarin, which showed the lowest yields throughout harvests (taBle 2 ).In general, these data are in agreement with the initial results obtained by Pompeu Júnior et al. ( 2013), working with most rootstocks studied in this research.
Significant differences were observed for the production efficiency from 2011 to 2015.The highest index, of 4.17 kg.m -3 , reached in the 2012 evaluation in plants grafted on 1710 citrandarin and the lowest in plants on 'Cleopatra' rootstock, with average values of 0.72 kg.m -3 in 2015.the highest eP values occurred due to the lower vegetative growth, which resulted in higher production per canopy area.In 2015, with seven-year-old plants, eP values ranged from 0.72 in plants on 'Cleopatra' to 1.77 kg.m -3 in plants grafted on '1708' citradia, a hybrid of trifoliate with sour orange (taBle 2).these results evidenced the ability of trifoliate to increase the productivity of acid lime in the region, provided that adjustments are made to the crop spacing.these values are lower than those reported by Stenzel and Neves (2004), who observed for a period of eight harvests in the state of Paraná in 'tahiti' IaC-5 plants grafted on 'Rangpur' lime tree, yield of 6.54 kg m -3 .aranguren et al. ( 2004) observed eP values for 'tahiti' plants grafted on C. macrophylla ranging from 1.0 to 1.7 kg m -3 under Cuban conditions.
Regarding juice yield, there were no significant differences induced by rootstocks in the three-year study period (taBle 3).these results differ from those obtained by Stenzel and Neves (2004), who observed higher RS in 'tahiti' lime tree grafted on 'Rangpur' lime.however, it is noteworthy that all rootstocks induced RS above 42%, which according to Hortibrasil (2000) classification is the minimum RS required for fruits for export.the RS results obtained are higher than those found by Stenzel and Neves (2004) these values were within the acceptable range for the domestic and export markets.the rootstocks evaluated did not cause significant differences in the acidity of 'Tahiti' acid lime fruits (taBle 3). the averages found were higher than those obtained by Stenzel and Neves (2004), who reported values between 5.0 and 5.8%, whereas in the present study, titratable acidity ranged from 6.00 to 7.52%, considering the three evaluations.these acidity levels are similar to those described by Stuchi et al. ( 2009) from 6 to 8%, which according to the authors, are close to the commercial standards demanded by the market, which is 7-8%.
Rootstocks induced significant variations in vitamin C levels (taBle 3) in the 2011 and 2012 evaluations.In 2013, there were no differences in values found.'1697' hybrid presented the lowest values in 2011 and 2012 (27.56 and 28.60 mg ascorbic acid.100ml -1 of juice, respectively).On the other hand, 'volkameriano' lemon, 'limeira' trifoliate, 'Carrizo' citrange and 'Sunki' mandarin rootstocks showed the highest values, ranging from 31.54 to 34.89 mg ascorbic acid.100ml -1 juice.On average, the results for vitamin C (tvC) found in the study were higher than those observed by miranda and Campelo Júnior (2010), who found average levels of 27.97 mg ascorbic acid.100ml -1 of juice in 'tahiti' lime fruits from Colorado do Oeste, RO. the high tvC found in 'tahiti' lime fruits are interesting, since marketing strategies can be adopted, emphasizing the importance of the consumption of nutraceutical foods.

CONCLUSIONS
'Rangpur' lime, 'volkameriano' lemon and 'Carrizo' citrange were the rootstocks that induced greater vegetative vigor and productivity to 'tahiti' acid lime.On the other hand, 'limeira' trifoliate and '1708' citradia induced lower vigor and higher production efficiency, and could be used as alternative rootstocks to 'Rangpur' lime, provided that adjustments are made in planting spacings in order to increase productivity.
In general, fruits presented physical and chemical characteristics within commercial standards.

TABLE 1 -
mean values of plant height (a) (m), diameters of rootstock stem (DCPe) and grafts (DCe) (mm), DCPe / DCe ratio, canopy diameter (DCO) (m) and mean canopy volume (vmC) (m³) from 2009 to 2015 of 'tahiti' acid lime grafted on 12 rootstocks.Jaíba, minas Gerais.Means followed by the same letter in the column for each year do not differ by the Tukey test at 5% probability level.

TABLE 2 -
mean values of production per plant (PP) (kg.plant -1 ), mean fruit mass (mmF) (g), number of fruits per plant (NFP) (un), productivity (PtvD) (t.ha -1 ) and production efficiency (PE) (kg.m -3 ) in 2010 to 2015 of 'tahiti' acid lime grafted on 12 rootstocks.Jaíba, minas Gerais.Means followed by the same letter in the column for each year do not differ by the Tukey test at 5% probability level.

TABLE 3 -
mean values of longitudinal diameter (Dl, mm) and equatorial diameter (De, mm) of fruits, juice yield (RS,% juice), total soluble solids (SST, ° Brix), titratable acidity (AT, % citric acid) and vitamin C content (tvC, in mg.100 ml -1 of juice) in 2011, 2012 and 2013 of 'tahiti' acid lime grafted on 12 rootstocks.Jaíba, minas Gerais.Means followed by the same letter in the column for each year do not differ by the Tukey test at 5% probability level.